The use of vacuum sources for recovering materials in a marine environment, particularly spilled fluid cargo on open water such as crude oil and associated debris, is well-known. Example of a typical device is disclosed in U.S. Pat. No. 3,813,887 to Kruger et al. Such devices typically use displacement pumps which pull the materials to be recovered through the pump itself.
Recent experience at the oil spill in Prince William Sound, Alaska shows that devices using displacement pumps are unsuited for such recovery work. The material that is to be recovered includes a great deal of debris, such as wood, dead animals, and pieces of cloth, as well as the spilled crude oil. Pulling this type of debris through a displacement pump causes frequent mechanical breakdowns with the attendant expense and time loss of repair. It is critical to recover the spill materials as soon as possible to minimize environmental damage as well as direct cost. Also, spilled petroleum products can develop into a material called mousse and clot as time passes, making recovery more difficult. Thus, these frequent breakdowns cause delays when time is critical.
Another problem is that devices for recovering fluid cargo spills usually not near the spill site and must be transported to it, causing delays in the initial recovery of the spill materials.
Of course, the most efficient way to limit damage from a fluid cargo spill is to minimize the amount of cargo spilled in the first place. Marine vessels transporting fluid cargos such as crude oil typically do not have systems to reduce the amount of cargo spilled that function very effectively. Examples of such systems are disclosed in U.S. Pat. No. 3,859,944 to Warner and U.S. Patent No. 4,241,683 to Conway. Warner discloses a system for transferring cargos from one hold to another, lining the holds with a puncture resistant liner, and automatically pressurizing a hold that has been breached to minimize the extent of a spill. Conway discloses the use of a three-dimensional grid of bulkheads and system for transferring cargo from one hold to another in the event of a breach to minimize lost cargo.
While these devices may minimize cargo spills somewhat, they may actually aggravate the problem under certain circumstances. For example, if a breach in a hold penetrated the liner in Warner, the automatic pressurization of the hold could actually force more fluid out of the hold. Also, systems like the one disclosed in Conway would require extensive additional construction on a vessel and would be difficult to retrofit.
As illustrated by the present discussion, there are a number of desirable features for an apparatus to minimize and recover fluid cargo spills in a marine environment. It would be desirable to have an apparatus that prevented or minimized the fluid cargo spill from a breach in a hold. In addition, it would be desirable for apparatus for spill recovery and spill minimization to be relatively inexpensive to install on new marine cargo vessels and to retrofit on older vessels. It would be desirable to have an apparatus for recovering materials in a marine environment using a vacuum source with a passage to a substantially airtight enclosure, such a marine cargo vessel hold that, in turn, has a pickup mechanism forming a passage between the enclosure and spill material to be recovered, so that the recovered materials pass directly into the enclosure without passing through the vacuum source. It also would be desirable to have an apparatus that could be installed on a marine vessel temporarily in the event of a fluid cargo spill or that could be installed on the vessel permanently. Further, it would be desirable to have an apparatus which could use a vacuum source to remove the sheen left on water after petroleum products have been released on the water.
While the above discussion was centered on apparatus for minimizing and recovering fluid cargo spills in a marine environment, it is not intended that the invention be limited to this situation. It will be obvious from the description that follows that the present invention will be useful in other applications with problems common to those described herein.